Method and apparatus for forming flexible corrugated members

ABSTRACT

A method and apparatus for converting smooth walled tubular members into corrugated flexible members. The invention contemplates stamping grooves of progressively increasing depth into the outer walls of the smooth tube and thereafter compressing the thus corrugated member while preventing deformation and expansion in the radial direction to thereby define a flexible tube characterized by a helically corrugated wall.

United States Patent Charvet July 23, 1974 METHOD AND APPARATUS FOR FORMING FLEXIBLE CORRUGATED MEMBERS [76] Inventor: Joseph Charvet, Dessancourt,

France [22] Filed: Apr. 30, 1973 21 Appl. No.: 355,521

Related US. Application Data [60] Division of Ser. No. 129,357, March 30, 1971, which is a continuation-impart of Ser. No. 738,215, June 19, 1968, abandoned.

[52] US. Cl. .Q. 72/77, 72/98 [51] Int. Cl B2ld 15/04 [58] Field of Search 29/454; 72/77, 98, 114

[56] References Cited UNITED STATES PATENTS 2,023,417 12/1935 Guarnaschelli 72/115 2,635,330 4/1953 Fentress 29/454 FOREIGN PATENTS OR APPLICATIONS 561,294 10/1957 Belgium 72/115 250,126 8/1947 Switzerland 72/114 171,843 0/1965 U.S.S.R 72/77 Primary Examiner-Lowell A. Larson [57] ABSTRACT A method and apparatus for converting smooth walled tubular members into corrugated flexible members. The invention contemplates stamping grooves of progressively increasing depth into the outer walls of the smooth tube and thereafter compressing the thus corrugated member while preventing deformation and expansion in the radial direction to thereby define a flexible tube characterized by a helically corrugated wall.

11 Claims, 3 Drawing Figures METHOD AND APPARATUS .FOR FORMING FLEXIBLE CORRUGATED MEMBERS CROSS REFERENCE TO RELATED APPLICATIONS This is adivision ofU.S. Pat.- application Ser. No. 129,357, filed Mar. 30, 1971. 1

This invention is a continuation-in-part of US. Pat. application Ser'. No.' 738,215, which was filed June 19, 1968, now abandoned claiming priority upon parent French Patyapplication Ser. No. l.ll,25'l of .June 21, 1967."

BACKGROUND OF THEINVENTION l. Field of the Invention walled, relatively rigid tubular'members'into corrugated, bendablemembers. More specifically, the present invention is directed to apparatusfor the formation of helical corrugations in the outer wall of a smooth tu- I bular member. Accordingly, the generalv objects of the j present invention are to provide novel andirnproved methods and apparatus ofsuch character. I 2 Description of the PriorArt Several methods are known in the prior art which en- I able smooth walledtubular members to be transformed into corrugated members characterized by flexibility,

' One of the morecommon prior art methods comprises the transverse deformation of'a cylindrical tube by forcing the wall thereof inwardly to the full depth of the desired finished corrugations and thereafter'applying longitudinalpressure to reduce the pitch of the corrugations. In this prior art method, as well as in other known techniques, no means are provided to limit the expansion in the radial direction of the folds formed in the tube walls-Similarly, prior art techniques didjnot,

provide means to insure uniform distances between the folds or corrugations while the longitudinal pressure required to reduce the pitchof the corrugations was applied. A further disadvantage of the prior art residedin the absence of meansfor uniform'lydistributing the applied longitudinal pressure amongst the successive folds of the corrugationtF inally, prior art methodsand apparatus for forming flexible corrugated tubes did not permit continuous operation. Y

I SUMMARY OF THE INVENTION refer to like two helicoidal convolutions which are concave in relation to the outer surface of the original tube. The second die or die portion effects the compression of the ularly'in-the space between two'successive concave convolutions, resulting from the stamping step. The

compression of the tubular member will preferably be progressive. v R 1 a a In accordance with a preferred embodiment of the invention, the die'or dies have theexternal form of a nut. Also, depending on the depth of the convolution and on the desired progressivity, the screw thread defined by the dies may comprise one or more convolutrons. I 1

' The second die or die portion,.as noted, performs a r i compression operation which progressively folds the This invention relates to the conversion of smooth wave or thread created by the stamping of the first die portion. The second die willftypically have aconstant bore diameter equal to the bore diameter at the outlet of the first die or die portion whereby there willbe no further radial stamping action as the member proceeds from the first die into the second die.' The second or compression die will preferably. be'characterized by a regularly decreasing'pitch which effects the compression of the flanks of the convolution.

The present invention may also comprise a .third die or die portion which verifies or finishes the contourof the finished product. When included, the third die or die portion will comprise a nut having an internal thread of constant pitch and of constant borediameter.

BRIEF DESCRIPTION OF THEDRAWING The present invention may be better understood and its numerous objects and advantages will'become apparent to those skilled in the art by reference to theaccompanying drawing wherein like reference numerals elements in the several figures and .in which:

- FIG. l is a cross-sectional view of a first embodiment of the inventionrtheembodiment of FIG..1 comprising a three die portions;

contact points with relation to the tubular member being deformed when relative movement of rotation and translation in the axial direction are'produced between the cylinder and the die.

Apparatus for practicing the method of the present FIG. 2 is a cross sectional view of a second embodimentof the invention wherein two die portions are utiliied; and r J a V FIG- 3 is a cross-sectional view of a third embodiment of the invention which employs three die portions formed in two die members.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Each of these dies is'characterizedby having the exter-' nal shapeof a nut; the three dies being respectively indicated by reference numerals, 1, 2 and 3. In operation,

the dies 1, 2 and 3 and the tubular workpiece 4 are rotated relative to each other about axis X-X. The requisite rotation is achieved through the use ofany suitable device'and thus the rotating means has not been shown in the interest of facilitating understanding of the invention. It is to beunderstood'that, during rotation, the

tubular member to a progressively increasing depth in the centriperal radial direction so as to provide at least dies 1, 2 and 3 are restrainedfrom translational motion in order to effect advancement of the workpiece in the downward direction asshown in FIG. 1.

' The first or uppermost die 1 is the stamping die and has an internal screw thread of constant pitch. However, the bore diameter of die l'decreases regularly proceeding from point 5 serially to points 6, 7 and 8.

The internal thread of die 2, which is the compression die, has a constant bore diameter defined by die sections 9 and 10. However, as can be seen through comparison of sections 11 and 12 of die 2, the bottom diameter of the thread increases in the direction of movement of the workpiece through the compression die.

The third or finishing die 3 comprises a nut having an internal thread with constant diameter and pitch as illustrated.

In operation, the dies are assembled and restrained to prevent translational movement along the axis X-X. Thereafter, either the dies or the workpiece, or both, are rotated about axis X-X' so as to cause the workpiece 4 to advance through the dies. This technique is, of course, different from the prior art and makes it possible to continuously machine tubes of much greater length than previously possible. That is, the present invention does not require internal support of the tubular member and thus may be practiced starting with a strip which is welded into tubular shape before it enters the dies; it thus being possible to operate continuously with rotation of the workpiece affecting its advance in stationary dies.

As will be obvious to those skilled in the art, the die 1 produces helicoidal waves of progressively increasing depth and of constant pitch in the outer wall of the tubular member 4. The die 2 effects the compression of the helicoidal waves by acting on the flanks thereof to produce a progressively decreasing pitch.

As noted above, because of the presence of die 2, the third or finishing die 3 has little effect on the finished product since die 3 does not act either on the pitch or the depth of the thread formed in the workpiece 4.

It will be observed that the screw threads of the three dies should constitute a continuing, non-interrupted thread. That is, preferably the end ofa thread in a preceding die should coincide with the beginning of the thread on the next succeeding die in the direction of workpiece advancement. In order to accomplish the foregoing, it will be advantageous for any discontinuity of the curve defined by the threads to be attenuated by special machining at the abutment points between the dies. It will also be observed that, when assembled, the two or three dies do not necessarily abut against one another along plain surfaces perpendicular to the axis of rotation.

With reference now to FIG. 2, it is to be noted that the disclosed embodiment comprises only the dies 1 and 3; the number of threads of die 3 being increased when compared to the embodiment of FIG. 1. While the compression die 2 has been omitted from the embodiment of FIG. 2, the apparatus achieves an equivalent result when compared to the embodiment of FIG. 1 by imparting a rotation about the common axis to die 3. Such a rotation causes an oblateness which results in a reduction of the pitch.

Referring to Flg. 3, a third embodiment is disclosed wherein the dies 1 and 2 have been combined in a sin gle nut 12. Nut or die 12 is comprised of portions 13 and 14 which correspond respectively to dies 1 and 2 of the embodiment of FIG. 1. The third or finishing die is shown in FIG. 3. It is, however, to be understood that the finishing die may be eliminated as discussed above.

It is to be emphasized that, depending on the materials to be machined, the present invention may be practiced by utilizing only the first and third dies or portions thereof as shown in FIG. 2. When the second or compression die is omitted, the third or finishing die performs the compression function. As noted above, this is accomplished by rotation of the third die about the axis X-X to provide an angular displacement relative to the position where the thread of the finishing die would form a continuation of the thread of the first or stamping die. In cases where the second die is omitted the compression will be severe and it is usually desirable to employ the second die in the interest of obtaining a more progressive compression.

In application, the present invention may be employed with workpieces of any deformable metallic or synthetic material. The steps of stamping and/or compression, particularly when the workpiece is comprised of a thermoplastic synthetic material, may be performed with the aid of suitable heating devices for the purpose of bringing the tubular member to the proper working temperature.

As will now be obvious to those skilled in the art, the present invention may replace previous equipment of similar character in existing machines. When compared to the prior art, which employs internal support shafts with their attendant disadvantages, the present invention eliminates the danger of twisting and the necessity of practicing the invention with a seamless tube or a redrawn welded tube. Also, since the dies of the present invention preferably have the external shape of a nut or nuts, assembly, disassembly and use of the present invention is considerably easier than that of previous tools. Similarly, fabrication of the tool is facilitated in accordance with the present invention.

As noted above, the present invention also has the added advantage of being capable of use to corrugate welded tubes. The present invention may also be practiced using strip which is continuously welded in order to form the workpiece. The latter advantage, in turn, permits the present invention to be practiced continuously thus .constituting a substantial advantage when compared to the prior art.

Accordingly, while preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the present invention. Thus, for example, the invention is not limited to the production of a'sinusoidal corrugation or to the production of folds or corrugations which are nearly in contact with one another. Thus, it is to be understood that the present invention has been described by way of illustration and not limitation.

What is claimed is:

l. A method of making corrugated tubing from tubular stock of indefinite and substantial length which comprises the steps of:

transversely compressing a substantially smooth walled cylindrical tube by forcing a portion of the wall thereof radially inwardly to the full depth of the desired finished corrugations to define a helical groove, the transverse compression being produced during continuous relative axial and rotational movement between the rube and a tool and without internal support of the tube;

the tubing which are subjectedto radial compression.

which radial expansion 3./ method of making orrugated from tubu lar stock of indefinite and substantial length comprising effecting continuou s progressive transverse'compression followed by1 continuous progressive'longitudinal compression of a rotating internallyunsupported tubular memberto produce successivefolds in the member wherein the longitudinal compressionis simultaneously performed on agrooved portion of apreviously'transversely compressed tubular member and wherein radial deformation and expansion of each of the successive folds resulting from the. transverse compression is pre-' vented on at least that portion of the member which is subjected to the longitudinal compression.

4. The method of claim 3 in which radial expansion and deformation of the folds resulting from the transverse compression is prevented between the portions of 5. A method of making corrugated tubing from tubular stock of indefinite and substantial length which comprises the steps of:

I the member which are subjected to radial compression.

continuously rotatingand progressively transversely deforming a cylindrical tubular member by forcing the wall thereof inwardly to the full depth of the finished corrugations, the transverse deformation being produced during relative movement between the tubular movement and an external-die. and

without internal support for the member; and subsequently applying continuous progressive :longi tudinal pressure to each'of the folds of the corrugation to continuously and progressively reduce the.-

pitch of the corrugations while simultaneously preventing deformation and expansion of the corru- 6 gated memberin'the radially outward direction at least on that portion of the corrugated member directly subjected to. the longitudinal pressure. 6. Themethodof claim 5 wherein the step of reducing the'pitch'of the corrugations includes:

applying an external counterpressure to the tubular member. M I 7. The method of claim'6 wherein the step of applying external counterpressure comprises: i

imposing a predete'rminedexterior shape'on the folds 'of the corrugation subjected to the reduction in pitch.

. 8, The method of claim '6 whereinthe step of applying an external counterpressure comprisesz' I imposing aconstant predetermined outer radial diameter at least on the corrugations subjected to thereduction in pitch.

9. A method of continuously making corrugated rub ing from a substantially smooth 'walled tubeof substantial length comprising the steps of: f continuously rotating and'displacing the tube with respect to an external forming die while simultaneously progressively transversely deforming the wall thereof along successive predetermined'portions of the length of the tube to the full depth of the desired corrugations; and

' thereafter applying to the corrugated portion, during a continuation of the displacement thereof, longitudinally controlled pressure to each of the folds to progressively reduce the pitch of the corrugations while preventing deformation and expansion in the radially 'outwarddirection only at least along the portion of the tube subjected to the reduction of pitch by applying an external counterpressure to the entire external surface of the "corrugations.

10. The method of claim 9 wherein the application of 7 external counterpressure comprises imposing a predetermined exterior shape on the folds of the corrugations subjected to the reduction in pitch.

11. The method of claim 9 wherein the step of application of external counterpressure comprises imposing, at least on the corrugations subjected to a reduction of pitch, a constant predetermined outer radial diameter.

-* g;;g UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTEGN Patent No. 3,824,826 Dated Jul 23 1974 Inventofls) Joseph Charvet V It is certified that error appears in the ebove-v-identified patent. and that said Lettere Patent are hereby corrected as shown below:

IN THE CLAIMS:

Claim 5, line 9 {column 5, line 38),

change "movement" to --member-- Signed and sealed this 26th day: of November 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. 0. MARs ALL DANN Attesting Officer commissloner of Patents 

1. A method of making corrugated tubing from tubular stock of indefinite and substantial length which comprises the steps of: transversely compressing a substantially smooth walled cylindrical tube by forcing a portion of the wall thereof radially inwardly to the full depth of the desired finished corrugations to define a helical groove, the transverse compression being produced during continuous relative axial and rotational movement between the rube and a tool and without internal support of the tube; simultaneously longitudinally compressing a previously transversely compressed grooved portion of the tube; and preventing deformation and expansion of the tube in the radially outward direction only during longitudinal compression.
 2. The method of claim 1 in which radial expansion and deformation of the folds resulting from the transverse compression is prevented between the portions of the tubing which are subjected to radial compression.
 3. A method of making corrugated tubing from tubular stock of indefinite and substantial length comprising effecting continuous progressive transverse compression followed by continuous progressive longitudinal compression of a rotating internally unsupported tubular member to produce successive folds in the member wherein the longitudinal compression is simultaneously performed on a grooved portion of a previously transversely compressed tubular member and wherein radial deformation and expansion of each of the successive folds resulting from the transverse compression is prevented on at least that portion of the member which is subjected to the longitudinal compression.
 4. The method of claim 3 in which radial expansion and deformation of the folds resulting from the transverse compression is prevented between the portions of the member which are subjected to radial compression.
 5. A method of making corrugated tubing from tubular stock of indefinite and substantial length which comprises the steps of: continuously rotating and progressively transversely deforming a cylindrical tubular member by forcing the wall thereof inwardly to the full depth of the finished corrugations, the transverse deformation being produced during relative movement between the tubular movement and an external die and without internal support for the member; and subsequently applying continuous progressive longitudinal pressure to each of the folds of the corrugation to continuously and progressively reduce the pitch of the corrugations while simultaneously preventing deformation and expansion of the corrugated member in the radially outward direction at least on that portion of the corrugated mEmber directly subjected to the longitudinal pressure.
 6. The method of claim 5 wherein the step of reducing the pitch of the corrugations includes: applying an external counterpressure to the tubular member.
 7. The method of claim 6 wherein the step of applying external counterpressure comprises: imposing a predetermined exterior shape on the folds of the corrugation subjected to the reduction in pitch.
 8. The method of claim 6 wherein the step of applying an external counterpressure comprises: imposing a constant predetermined outer radial diameter at least on the corrugations subjected to the reduction in pitch.
 9. A method of continuously making corrugated tubing from a substantially smooth walled tube of substantial length comprising the steps of: continuously rotating and displacing the tube with respect to an external forming die while simultaneously progressively transversely deforming the wall thereof along successive predetermined portions of the length of the tube to the full depth of the desired corrugations; and thereafter applying to the corrugated portion, during a continuation of the displacement thereof, longitudinally controlled pressure to each of the folds to progressively reduce the pitch of the corrugations while preventing deformation and expansion in the radially outward direction only at least along the portion of the tube subjected to the reduction of pitch by applying an external counterpressure to the entire external surface of the corrugations.
 10. The method of claim 9 wherein the application of external counterpressure comprises imposing a predetermined exterior shape on the folds of the corrugations subjected to the reduction in pitch.
 11. The method of claim 9 wherein the step of application of external counterpressure comprises imposing, at least on the corrugations subjected to a reduction of pitch, a constant predetermined outer radial diameter. 